


It Burns

by MissKierie



Category: Undertale (Video Game)
Genre: Double Penetration, F/F, F/M, Group Sex, M/M, Mating Cycles/In Heat, Multi, Sexy skeletons, Sibling Incest
Language: English
Status: Completed
Published: 2019-10-27
Updated: 2019-10-27
Packaged: 2021-01-13 17:48:26
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,092
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21193160
Author URL: https://archiveofourown.org/users/MissKierie/pseuds/MissKierie
Summary: One-off extremely vile smut featuring everyone's favorite weird asshole: Sans! He's in heat and it sucks and he'll do just about anything to get some relief.





	It Burns

**Author's Note:**

> idea came from @mellednsfw on twitter here: https://twitter.com/i/web/status/1120101489538678786

you are disgusting.

you’re in the throes of pulsing, semi-annual heat. it affects every monster differently. for some, just an increased libido— easy to snuff out with a few flings. some develop an overwhelming urge to breed, and after dropping their load in a fertile receptacle, they’re satisfied. but for some, like you, only fulfilling a deep, carnal fantasy can offer relief.

deep down, at the core of your being, you want to fuck your brother. with each successive heat, you’ve satisfied every scenario your twisted mind could come up with. it started simply enough— a threesome, having sex in public, some light bondage. but your well of erotic fantasies is running dry. and now all you have are thoughts of Papyrus, the only family you have left.

frustrated tears stream down your face as you jack yourself off. thinking about him, your baby bro, pushing himself inside you as he kisses you. it’s so fucking fucked. biting a pillow as you fuck your fist— he’s right in the other room, he can’t hear you, he can’t know. the tension inside you hasn’t lessened one bit since you started masturbating, an hour ago. you’ve climaxed a few times, but no, nothing helps. everything hurts and everything turns you on, but nothing gives any relief.

sniffle and wipe your messy face on your sleeve. you’re drenched in sweat and cum. this fucking sucks. you hate yourself.

you just lie there for a while, vegetating. your dick keeps throbbing. magic begging for attention. weighing your options…

you didn’t want it to come to this. this was your last resort. but you need someone to help you with this heat. you might do something stupid, like steal his clothes to pretend he’s really fucking you, if you stay here. Paps doesn’t deserve anything like that.

you kick off what you’re wearing and slip on a less filthy pair of shorts and a t-shirt. your brother just washed your favorite jacket and you put it on. just the feeling of your arm sliding through the tunnel of your sleeve is enough to give you chills. even the smell of the fresh laundry turns you on, knowing he touched it not long ago.

at least you don’t have very far to go.

Grillby’s is bumping this time of night. it’ll be packed, and loud, maybe no one will even notice if you decide to… with a quivering hand, you push the bar door open.

everyone turns to smile and wave at you as you step inside. but you must be making a weird face or something, cuz they all quickly get quiet.

you stop walking, frozen by sudden social anxiety as everyone fucking stares. do they know? are you so deep in this heat that they can tell just by looking at you?

Doggo appears next to you, grabbing your arm. the physical contact alone sends a jolt of arousal through you. how could he see you? you weren’t moving.

his nostrils flare as he takes a deep whiff of you. He says, “I don’t need to see you. I could smell ya a mile away.”

gulp, okay, maybe this wasn’t such a good idea. get out, sans, just leave. “uh, new cologne,” you offer, “a sample from a magazine. don’t bother reading it though, it stinks.”

most of the bar patrons give a chuckle at the joke, the tension lessons, and almost everyone has returned to their own business.

except the members of the Royal Guard. Doggo’s grip on your forearm lessens. “Hey Sans, are you okay?” he asks with genuine concern.

that question makes you completely break down. you weren’t expecting it and you are very much not okay. you manage to keep it together to not make a scene, but just barely.

“n….. no, “ you finally peep out. slowly, you grab the bottom of your shirt and pull it up, exposing your ribs and the beating, swollen, throbbing magic concealed within your soul. “i need help.”

Doggo’s eyes widen and Dogaressa turns to her partner to whisper something in his ear. all 5 of the dogs' tails are wagging.

then, Doggo steps into you, leaning down to run his tongue across your sweaty brow as his warm hands run across your ribs. “I got you,” is all he says.

those simple interactions feel so fucking good after days of building heat and you loudly moan out your approval.

Hey, the bartender suddenly says, Take it out back. Grillby can deal with some heavy petting and make outs in his booths, but it’s obvious these dogs have much more in mind.

with Doggo’s scruffy hands still on you, it’s hard to listen to what Grillby just said. when the dog grabs your wrist, it suddenly hits you.

“not outside,” you almost whine, sounding more pathetic than you anticipated. your house is right next door, Papyrus might hear you if they take you to the back alley.

Dogamy and Dogaressa stand up, holding each others paws as they walk to the kitchen door on the left, behind the bar. they both turn to you and smile before they disappear behind it. Greater and Lesser Dog are watching, but don't get up to join them.

no words are needed— Doggo leads you after the couple, through the door, past the kitchen, and to the giant metal door at the end of the hallway. it's the walk-in fridge and you have to smirk; absolute fucking genius. sound proof, secluded, and the floors will be mopped when they clean it next anyway. the handle's already ajar, Doggo just pulls it open and you both slip inside.

the door clangs shut behind you. it's dead quiet, except for the whirring of the motor running the fridge. pitch black, too, the only light is the glowing red bulb above the door, presumably an alarm system for the temperature.

two warm bodies are suddenly pressed against you and you jump, startled, but you cut the tension with a fluttery laugh. "hey guys," you say, reaching to touch the dog hugging you, your palms filled with a nice pair of tits.

"So warm!" Dogamy huffs behind you. yea, with this heat, you don't even notice the cold of the refrigerator.

"(Poor thing, he needs help,)" Dogaressa chimes right after. she encourages you to reach into her cloak, and you grope her soft chest as she leans down to kiss you.

you nearly choke on her long tongue when Doggo crouches next to you three and brazenly pulls your shorts down. he slips his head between you and Dogaressa, licking across your dripping pubic arch. you haven't even manifested any genitals yet but FUCK it feels so good. you moan loudly into Dogaressa, holding onto her as her husband grinds his already hard cock into your tailbone.

you needed this, this is exactly what you needed. to be a plaything to your co-workers, in a public place where anyone could walk in at anytime. the tight coil inside you is still taut, but you can feel it starting to unwind.

Dogaressa is reaching around you into Dogamy's cloak, starting to stroke his cock while Doggo snorts and laps frantically at your pubis. you've managed to manifest a cock and Doggo wraps his tongue around it. embarrassingly, you immediately climax, shooting out jets of blue cum on Doggo's face and Dogaressa's gown. she giggles at you and you laugh back, giving yourself a few moments to bask in the orgasm before the heat comes right back.

"Nowhere near done yet," Dogamy grumbles into the back of your skull, his hips thrusting into Dogaressa's hand.

"(Just getting started,)" Dogaressa echoes. she lifts her leg up and rests it on your hip, inviting you to reach between her legs. your dominant hand teases at the fur of her inner thighs while Doggo closes his muzzle around your still throbbing dick.

"Make something soft for me, pup," Dogamy says behind you and his hot breath makes you shiver. easily, you conjure up a plump, round ass, electric blue ectoplasm, providing the only other light source in the cooler.

there's so much going on, you're getting overwhelmed. you can smell Dogaressa's arousal, feel her fur getting wet with sweat and excitement. Doggo's head is bobbing on your cock, both hands groping your trembling thighs. Dogamy is grinding his length between your checks and you can feel the massive bulb of his knot.

it’s not enough, you’re still in pain. “put it in,” you breathe against Dogaressa. she leans into you and you think she’s about to kiss you, but her nose bumps against her husbands instead. you just grin at the spectacle of them nuzzling like champs and Doggo’s ears swaying as he sucks you off.

Dogaressa reaches around you, grabs your ass, and spreads you as her claws coyly dig into you. you arch your spine as Dogamy slowly starts slipping his bare shaft inside you. he isn’t lubed, but his canine cock is covered in enough wetness that it spears you easily.

“aahhn, fuck!!” you shamelessly cry out as Dogamy thrusts until you meet his knot. you are nowhere near prepared enough to take a dick this big and it hurts in the absolute best way, in the way you deserve.

it feels so fucking good to finally have another monster with their own pulsing arousal to fill you. your eye ignites with magic, as if him entering you meant you could finally release some of the tension that this heat has been building.

he starts bucking immediately, inches of cock slamming into your glowing blue ass so hard you can feel him rubbing against your tailbone.

you’re so distracted at the feeling of your ass being torn apart that you don’t notice the absence of Doggo’s mouth around your swollen dick. but you do notice that being replaced by something much softer and warmer—Dogaressa’s cunt.

your head snaps forward to stare at Dogaressa blankly, so struck with overwhelming please at both ends of you that your sockets just go blank.

she giggles at that and leans down to kiss you as she starts moving. “(What’s wrong, Sans? To _ruff_ for you?)” her wet tongue runs against your teeth. dog breath.

she actually barks the rough line and you have to share the laughter.

“n-no, im just _mutts_ about you.”

“Alright alright,” Doggo says on your right side, standing right next to you, paw playing with his dick casually. it’s **huge**. he’s huge, he towers over all three of you. “Keep moving, so I can see.”

the dogs oblige, Dogamy slowly stretching your hole as he fucks you. more and more of his knot slowly makes its way inside as his hips slap against your ass. his wife wraps her arms around your shoulders for support as she bucks herself forward. her cunt is tight and wet, muscles pulling at the foreskin of your ectoplasmic cock. you grab one of her legs and lift it up, immediately finding a better angle. she growls and giggles again, gritting her teeth as she pushes back against and with your thrusting magic.

“She needs a bigger cock, skeleton,” Dogamy grumbles behind your skull, “she’s a bitch, not your delicate brother.”

through the haze of carnal desire, hearing him talk about your brother ignited a blazing rage inside you. “d o n ' t f u c k i n g t a l k a b o u t my br—ggaaahhh!!!”

you can’t keep up the morbid voice after Dogamy forces his entire knot inside you, blasting your insides with cum as he swells so much he’s literally trapped inside you. it hurts!!! it hurts so fuckin much!!! you can feel him grinding against the inside of your pelvis, he’s completely filled you!

you whimper as the cum slides down your femurs. Dogaressa keeps fucking herself against you, making sure you’re well and fully skewered on her husbands dick. it all feels too good and you revel in the complete indulgence of it all.

the dog behind you just pants and throbs while still inside you, his wife bucking so hard into you that it forces Dogamy back into one of the kitchen shelves, a box of frozen french fries landing on the floor.

you do make your dick bigger for her along with adding a knot, and eventually she cums on you. she pants excessively in your face, but you don’t mind the breath as the feeling of her tight muscles milks you of another orgasm.

“h-holy fuck,” you practically whimper as she pulls back from you, giving you a good look of her throbbing cunt, your blue jizz looking nice against her pink labia and white fur.

before you can even catch your breath, Doggo nudges between you and Dogaressa, massive red cock in one hand and he takes yours in his other, giving you a few long strokes.

everything is a bit hazy, another cock pushing at the space between your ass and cock, and your magic follows along, making a suitable slit for the monster to enter. you are so full and high on sex that you don’t even notice Dogaressa quietly slip out of the cooler.

both dogs pant as they hug you between them, flecks of saliva hitting your face as you find yourself almost unable to make a sound. it's so much, they're so big inside you, it's too good, you can feel the thin layer of ectoplasm separating them so clearly. like a thin piece of paper between two rubbing fingers, so hot, so much friction, but so wet with cum and ectoplasm.

you couldn't count the orgasms if you tried— each one rolls over you, punches you in the face, blends into the other, your holes spasming around their pumping shafts. so deep, you swear they were thrusting into your ribcage. one goes in, the other slides out, you aren't given a second to catch your breath.

"thank you," you manage to get out as Doggo pumps a final string of white jizz inside your torso. your belly is so full, it leaks out of your ectoplasm and coats the inside of your t-shirt, dripping down your spinal column and into the floor.

finally, you feel better. the oppressive urge to fuck and be fucked sated, for now at least. you rub your eye sockets with the sleeve of your jacket and have to laugh once you actually get a good look at the situation.

"you know what they say… there's nothing in the world friendlier than a wet dog," you jeer, nudging Doggo's sweaty muzzle with your forehead. they offer a light chuckle as they both leave your holes, causing that familiar aching emptiness to continue gnawing at you. it's fine. you can ignore it. you fumble to zip up your jacket, managing to hide most of your body inside the baggy fabric.

"We'll take you home. Doubt you can walk." Dogamy says as he hands you off to Doggo, so he can fix his cloak and look as presentable as possible before stepping outside. you promise yourself you'll be back tomorrow to clean the cooler floor. but you know, deep down, you won't do it.

you feel like a fucking babybones, being carried half naked by Doggo out the back enterance, down the alley, and to your house next door. it's snowing lightly, each flake reflecting the light of the lantern on your front porch.

Dogaressa opens your front door and you're immediately taken aback. "what are you doing in my house? don't tell me you're taking my bro's special attacks."

she grins knowingly and scurries out as soon as you step in. close the door behind you. take a deep breath.

out of the darkness, familiar hands take hold of your wrists. your eyes widen as you look up to see the glowing orange pupil of your younger brother.

"P-papyrus??!"

oh no, oh no, he caught you, what did that bitch tell him? he leans in and presses his warm teeth against your sweaty forehead.

"DOGARESSA TOLD ME EVERYTHING! SANS, WHY DIDN'T YOU COME TO ME FOR HELP???"

what? tears immediately start flowing down your face, shame, humiliation, knowing you smell like dog and that you still hold all their loads of cum inside you. but worst of all, the burning heat is back, the flame brighter than ever, your ultimate fantasy/nightmare within reach, his phalanges are fucking trembling around your wrists.

"d-don't, i don't, i, aah—" you're cut off as Papyrus drags you to the floor by your jacket and you can see the brilliant flash of his orange cock before he buries it into the throbbing magic between your legs. lying on your back, you cry out, feeling cum squirt out around his dick, and you grab onto him for dear fucking life.

"I FEEL IT TOO, BROTHER," Pap whimpers as he leans over you, "THE BURNING! THE PAIN!!! I DIDN'T KNOW, I'M SO SORRY!"

**_what???_** you burst out laughing. "you're sorry? i'm— nn!! we shouldn't, this is wrong, oh fuck! bro, that feels—!" he's ramming into you so hard, his pelvis smacking against yours, the heat from his magic melting so perfectly with yours. "please, please don't stop!"

Papyrus cradles you beneath him as he completely loses himself in your pussy. he keeps apologizing, "I'M SORRY, I CAN'T HELP IT!!! THIS IS THE FIRST TIME, THE FIRST TIME IT'S FELT BETTER!"

"it's okay, i'm h-here…"

he shot load after load of magic inside you, spent a good hour or so just using your hole until you passed out. you had no idea Papyrus had heats too, let alone one's as bad as yours…

the next morning was normal. he made waffles with whipped cream. he bent you over the kitchen table when you were done eating, slamming into your body so hard that the table scratched the paint off the wall. he was really ashamed of letting his 'MANHOOD' get the better of him, but you said it was a good excuse to repaint the walls.

"chartreuse," you say when he asks what color.

he sneers at you, "NO. YOU ONLY SAID THAT BECAUSE IT'S A FUNNY WORD."

"bro, my feelings," you choke while grasping at your chest, "you've blown them to smither-_greens_."

his sneer turns into a lustful smile, "ONE MORE PUN AND I'M MAKING YOU BE ON TOP NEXT TIME."

"c'mon, pap… you know i'm afraid of heights, a _yellow-bellied_ coward. you wouldn't do that to me."

yes, he would.


End file.
